A recent cluster of severe respiratory illness linked to the cruise ship MV Hondius has renewed global attention on hantaviruses, and raised specific questions for countries closely connected to international travel hubs — including Malaysia.
Unlike most hantaviruses, which are transmitted from rodents to humans through contaminated urine, droppings or dust, the Andes virus stands out because it has been documented to spread between people after close, prolonged contact.
The World Health Organization’s report of cases and deaths associated with the MV Hondius, together with the possibility of limited person‑to‑person transmission, makes this more than a routine zoonotic spillover, it is a public‑health event that requires careful clinical vigilance, coordinated laboratory investigation and targeted contact tracing.
To help Malaysian clinicians, public‑health professionals and the wider public understand the health, scientific and practical implications, we spoke with Associate Professor Dr Vinod Balasubramaniam, molecular virologist at Monash University Malaysia.
Dr Vinod explains what hantaviruses are, why Andes virus behaves differently from the hantaviruses more familiar in Asia, how infections present and progress, and what realistic risks and surveillance priorities Malaysia should adopt in response to this rare but consequential cruise‑ship outbreak.
Q: What is hantavirus, and why has the MV Hondius outbreak attracted global attention?
A: Hantaviruses are a group of rodent-borne viruses that can cause severe human disease after exposure to urine, droppings, saliva, or contaminated dust from infected rodents. Most human infections occur through environmental exposure rather than casual person-to-person spread. The MV Hondius outbreak is unusual because it occurred in an international cruise setting, involved severe respiratory illness, and has been linked to the Andes virus, a New World hantavirus associated with hantavirus pulmonary syndrome.
WHO reported a cluster of cases linked to the cruise ship, including deaths, and noted that human-to-human transmission cannot be excluded in this event. Clinically, hantaviruses are best known for two major disease syndromes: haemorrhagic fever with renal syndrome, more commonly associated with Old World hantaviruses in Asia and Europe, and hantavirus pulmonary syndrome, more commonly associated with New World hantaviruses in the Americas.
Andes virus belongs to the latter group and is associated with severe pulmonary and cardiopulmonary disease. Centre for Disease Control and Prevention (CDC) notes that Andes virus can cause hantavirus pulmonary syndrome and is the only hantavirus clearly known to spread person-to-person.
Q: How does hantavirus normally transmit?
A: The classical transmission route is rodent-to-human spillover. Infected rodents usually remain chronically infected and shed virus in urine, droppings and saliva. Humans are infected when contaminated material is disturbed and small particles become aerosolised, allowing the virus to be inhaled.
This can happen when cleaning storerooms, sheds, farms, plantation areas, campsites, warehouses, long-closed rooms, or rodent-infested spaces. Infection can also occur if contaminated rodent material contacts broken skin or mucous membranes of the eyes, nose or mouth.
CDC prevention guidance specifically warns that when fresh rodent urine, droppings or nesting material is stirred up, the virus can get into the air and infect people who breathe in the contaminated air.
Q: Why is Andes virus different?
A: Most hantaviruses do not transmit efficiently from person to person. Andes virus is the critical exception. It is endemic in parts of South America and has been linked to documented human-to-human transmission, especially after close, prolonged contact with a symptomatic patient.
CDC describes this as limited to close contact, including direct physical contact, prolonged time in close or enclosed spaces, and exposure to body fluids. Importantly, CDC also notes that people are typically infectious while symptomatic, not during long asymptomatic periods.
This distinction is central to the MV Hondius story. WHO reported that the cluster involved severe respiratory illness, deaths, and suspected or confirmed hantavirus infection, and specifically noted that limited human-to-human transmission had been reported in previous Andes virus outbreaks.
WHO also assessed the global risk as low, while recognising that the outbreak required coordinated international investigation, isolation, laboratory testing, contact tracing and medical evacuation.
Q: What happens after the virus enters the body?
A: After inhalation or mucosal exposure, hantaviruses can infect endothelial cells, which line blood vessels. The severe disease is not simply due to direct destruction of tissue. Much of the pathology appears to involve immune-mediated endothelial dysfunction, increased vascular permeability, capillary leak, pulmonary oedema, shock and, in some hantaviruses, renal involvement.
This explains why patients may begin with non-specific fever, muscle aches, headache or gastrointestinal symptoms, then deteriorate rapidly into respiratory distress, pneumonia-like illness, acute respiratory distress syndrome or circulatory shock. In the MV Hondius cluster, WHO described fever, gastrointestinal symptoms, rapid progression to pneumonia, ARDS and shock.
Q: Will the virus get into Malaysia?
A: The most scientifically defensible answer is: it is possible for an infected or exposed traveller to enter Malaysia, but sustained transmission in Malaysia is currently unlikely.
There are three theoretical pathways. First, an exposed traveller could enter Malaysia during the incubation period and later develop symptoms. This is plausible because the incubation window can extend for weeks.
Singapore’s Communicable Diseases Agency stated that two Singapore residents linked to MV Hondius were isolated and tested, and if negative would still undergo quarantine and extended surveillance for up to 45 days from last exposure. This matters for Malaysia because Malaysia and Singapore are highly connected through daily movement, family travel, work travel and tourism.
Second, if the virus is truly Andes virus, limited onward spread could occur through close contact with a symptomatic patient. This does not mean casual spread in malls, airports or public transport is likely. The risk would be highest for household contacts, intimate contacts, caregivers, healthcare workers without adequate precautions, or people sharing close enclosed spaces with a symptomatic case. Reuters also reported that countries were tracing passengers to prevent further spread and noted that hantavirus is usually rodent-borne but can rarely transmit person-to-person.
Third, local establishment of Andes virus in Malaysia would require a compatible animal reservoir. This is the least likely pathway. Andes virus is associated with South American rodent reservoirs.
Malaysia has rodents and has some evidence of hantavirus exposure historically, but that does not mean Andes virus is established here. Earlier Malaysian studies found serological evidence of hantavirus infection in humans and rodents, suggesting that hantaviruses are not irrelevant to Malaysia, while Sarawak surveillance found no detectable hantavirus circulation in the sampled rodent populations or levels below detection.
Q: What should Malaysia watch for?
A: Malaysia should not frame this as an imminent outbreak, but as a diagnostic and surveillance issue. The risk is low, but an imported case is possible. Clinicians should ask about recent cruise travel, South America travel, MV Hondius exposure, contact with confirmed or suspected cases, rodent exposure, and cleaning of rodent-contaminated spaces.
Hantavirus should be considered when a patient has fever, myalgia, gastrointestinal symptoms, thrombocytopenia, dengue-negative febrile illness, renal impairment, unexplained shock, or rapidly progressive respiratory disease. This is particularly relevant because Seoul hantavirus infection has previously been reported in Malaysia mimicking dengue fever.
Conclusion:
“The most likely way hantavirus enters Malaysia is not through local rodents suddenly spreading Andes virus, but through an exposed traveller during the incubation period. Even then, the probability of sustained community transmission is low, because Andes virus does not spread like COVID‑19. The concern is targeted: close contacts, delayed diagnosis, and missed cases that resemble dengue, leptospirosis or other tropical febrile illnesses.”, Dr Vinod emphasised.
In short, Malaysia’s priority should be measured vigilance rather than alarm. Public‑health responses must focus on prompt case recognition, careful contact tracing of close and prolonged exposures, and clear guidance for clinicians to consider hantavirus in severe or atypical febrile and respiratory presentations—especially when travel history or cruise‑ship exposure is present.
Strengthening diagnostic pathways and protecting frontline healthcare workers will help prevent small clusters from becoming larger problems, while avoiding unnecessary disruption to travel and trade.
Expert insights in this interview were contributed by Associate Professor Dr Vinod Balasubramaniam, Molecular Virologist and Leader, Infection and Immunity Research Strength, Jeffrey Cheah School of Medicine & Health Sciences, Monash University Malaysia.
The post Hantavirus, Andes Virus, and Malaysia: Why a Rare Cruise-Ship Outbreak Matters —Virologist Explains first appeared on PP Health Malaysia.